Synthesis models of the diffuse Cosmic X-ray Background (CXB) suggest that it can be resolved into discrete sources, primarily Active Galactic Nuclei (AGNs). Measuring the CXB accurately offers a unique probe to study the AGN population in the nearby Universe. Current hard X-ray instruments suffer from the time-dependent background and cross-calibration issues. As a result, their measurements of the CXB normalization have an uncertainty of the order of ∼15%. In this paper, we present the concept and simulated performances of a CXB detector, which could be operated on different platforms. With a 16-Unit CubeSat mission running for more than two years in space, such a detector could measure the CXB normalization with ∼1% uncertainty.